^aDepartment of Geological Sciences, Institute for the Study of the Continents, Cornell University, 3124 Snee Hall, Ithaca, N.Y. 14853, USA

^bMainz University, Germany

^cTectonics Special Research Center, The Universiy of Western Australia, Nedlands 6907, Western Australia

^dDepartment of Geology, University of Leicester, Leicester LE1 7RH, UK

^eDepartment of Earth Science, National Institute of Polar Resaerch, 1-9-10 kaga, Itabashi-ku, Tokyo 173-8515, Japan